Sima sells x biscuits and y cakes.

(a(i)) She sells at least 100 biscuits. Write an inequality in x. [1]

(a(ii)) She sells at least 120 cakes. Write an inequality in y. [1]

(a(iii)) She sells at most 300 biscuits and cakes altogether. Write an inequality. [1]

(a(iv)) Profit is 40 cents per biscuit and 80 cents per cake. Total profit is at least \$160. Show \(x+2y\ge400\). [1]

(b) Draw the four boundary lines and shade the unwanted regions. [6]

(c) Calculate her maximum profit in dollars. [2]